The main objective of the research is to further elucidate the nucleocytoplasmic feed-back controls which regulate genetic expression and to determine in particular the differences in the controls which operate at the post-transcriptional nuclear level. To attain this objective we shall purify and characterize the cytosol proteins which modulate mRNA release from isolated nuclei, and determine their site of action. This will involve the monitoring of the release of specific mRNA's and the equating of this release with specific cytosol proteins. The interaction of the proteins with specific messengers will also be investigated.